1. Field of the Invention
The invention relates to the method of using tablets by professionals and laboratory technicians within the optical and ophthalmic industry to introduce tints, UV absorbers, conditioners and other chemicals into heated and non-heated dyebaths in order to color, impart a UV blocking characteristic, decolor and provide other chemical treatments to plastic optical non-contact spectacle lenses and optical filter materials.
2. Description of Related Art
Within the optical lens and optical filter manufacturing industry, it has been a widespread practice to color, UV protect, hard coat, decolor, condition, clean and otherwise chemically treat plastic non-contact spectacle lenses and filters after manufacture in accordance with the customer""s cosmetic preference. Numerous techniques have been used to introduce tints, UV absorbers, decolorants, conditioners and other chemicals into the dyebaths used for tinting and otherwise treating non-contact spectacle lenses and filters. The most common technique is to use a concentrated liquid solution, although tint, UV absorber, decolorant and other chemical powders and capsules of such powders have also been employed. All of these techniques have the drawback of poor control over the concentrate. Concentrated liquids and powders can be spilled easily. The capsules or other packages can be torn, spilling out their contents, which can then become airborne. The quantities being introduced into the dyebath are often not precisely known. An examination of the various manufacturers of tints, UV absorbers, decolorants and other chemicals for ophthalmic lenses and filters shows many producers of liquid concentrate tints, UV absorbers, decolorants and other chemicals such as Brain Power Incorporated, Action, et. al. Most of these companies also produce the same materials in powder form, often encapsulated in a capsule or dissolvable plastic pack. The use of tablets or coated tablets to introduce ophthalmic tint, UV absorber, decolorant, conditioner or other chemical concentrate into plastic non-contact spectacle lens and optical filter tinting dyebaths, however has not been employed.
The tablets are dropped into the dyebath where they dissolve, providing the desired solution. This tablet method is an improved technique for introducing tint, UV absorber, decolorant, conditioner, hardcoating or other chemical concentrate into dyebaths for the treatment of optical non-contact spectacle lenses and filters. The tablets occupy less volume than corresponding liquids or powders and are more easily stored and shipped.
The tablets are more rugged and thus safer from the standpoint of spillage. An additional coating may be applied to the surface of the tablet in order to provide even better containment of the material within the tablet. The coating on the tablet also reduces oxidation, hydration and other chemical changes of the chemicals in the tablet. There is less chance of the material becoming airborne than in the case of powders, so the use of tablets is cleaner and safer from both a fire and health standpoint. The tablets come in a predetermined size, so that measurement of the amount of tint, decolorant, UV absorber or other chemical to be used consists of simply counting the number of tablets or scored fractional pieces of tablet to be used. No weighing or liquid measure techniques are needed. Accordingly, several objects and advantages of the tablet method for introducing tint into dyebaths are:
(a) to provide an extremely compact means for supplying tint, UV absorber, decolorant, conditioner and other ophthalmic chemical concentrate for the ophthalmic and optical filter industry;
(b) to provide a means for better control of the tint, UV absorber, decolorant or ophthalmic chemical concentrate as it is handled;
(c) to provide more precise measurement of the quantity of tint, UV absorber, decolorant or ophthalmic chemical being introduced into the ophthalmic lens and filter tinting dyebath;
(d) to allow for the precise mixing of different colors using multiple tablets of different colors and weights and strengths;
(e) to increase shelf life of the tints and other chemicals which would otherwise be affected by oxidation, hydration and other chemical changes since tablets and coated tablets have low surface areas.